Test equipment for testing an additional center tank (act) system of an aircraft

ABSTRACT

The present invention provides test equipment for testing an additional center tank (ACT) system of an aircraft. The ACT system comprising control means configured to perform functions of an Auxiliary Fuel Management Computer (AFMC) and an Auxiliary Level Sensing Control Unit (ALSCU). The test equipment comprises at least one test module adapted for coupling to the ACT system in place of at least a portion of the control means, the test module comprising means for generating one or more test signals and outputting the test signals to the ACT system.

The present invention relates to test equipment for testing anadditional center tank (ACT) system of an aircraft.

Modern cargo and passenger aircraft may be provided with an additionalcenter tank (ACT) system to supplement the main fuel tank system. TheACT system may include one or more additional center tanks, all of whichare located in the fuselage of the aircraft. The Airbus™ aircraft modelA319CJ, for example, may be fitted with up to six additional centertanks. The main fuel tank system is typically comprised of one or moretanks in each wing and a center tank in the fuselage of the aircraft.

An ACT system incorporates numerous valves needed for fuel delivery toand from the ACTs and between the ACTs (during refueling and defuelingas well as during in-flight fuel transfer) and for venting the ACTs.Examples of such valves are a fuel inlet valve for each additionalcenter tank, one or more transfer valves for feeding fuel into theadditional center tanks from the main tank system, one or more refuelvalves for filling up the additional center tanks on the ground, one ormore air shutoff valves for controlling flow of pressurized air into theadditional center tanks, etc. Persons versed in the art will begenerally familiar with the construction and operation of ACT systems inaircraft, especially those of the Airbus™ model series.

While fuel management of the ACT system may be performed by controlmeans common to the main fuel system and the ACT system, aircraft areknown to exist where dedicated control means are provided for this task.One such model is the above Airbus™ A31CJ. The dedicated ACT controlmeans may comprise an Auxiliary Fuel Management Computer (AFMC)operating together with an Auxiliary Level Sensing Control Unit (ALSCU)via a network of relays. The AFMC, inter alia, controls auto transfer ofACT fuel to and from the main center tank and between the ACTs in amanner balancing the aircraft during transfer and ensuring that thecenter of gravity of the aircraft remains within limits.

Level sensors associated with the ACTs sense the presence of absence offuel at various levels within the tanks. Specifically, the tank levelsensing system may include a high level sensor in each ACT to sense tankcontents at high level and end refuel of that tank. It may furthercomprise low level sensors to sense low level tank contents. The ALSCUprocesses the measured fuel levels and performs a comparison of lowlevel sensor wet states to monitor whether the ACT fuel transfer isprogressing in the correct order and if not to trigger a cockpitwarning. Accordingly, the ACT level sensors and the ALSCU are involvedin monitoring transfer of ACT fuel.

The ALSCU may also contain logic associated with the detection of damageto the forward ACT vent and refuel/transfer lines and their subsequentisolation.

The AFMC additionally receives fuel quantities and other informationrelated to the main tank system from a Fuel Quantity Indicating Computer(FQIC). The AFMC uses the information it receives from the ALSCU and theFQIC to calculate ACT and total aircraft fuel quantities for output toan Electronic Centralized Aircraft Monitor (ECAM) in the cockpit and toother receivers and also for control of automatic refuel of the ACTs.

The AFMC and ALSCU may be separate units to be connected to separatededicated plug-in interface sockets of the ACT system. It may be alsoenvisaged for the AFMC and ALSCU to be combined in a single controlunit.

Predelivery tests as well as ground tests during normal maintenanceprocedures require, inter alia, checking the ACT valves and/or the AFMCand/or the ALSCU for correct operation, i.e., whether the respectivecomponents properly react to certain conditions and/or to certaincommands. The commands may include valve commands manually initiatedfrom the aircraft cockpit. For example, in response to an inlet valveactuating command, a corresponding signal must be produced to cause somekind of indicating means, e.g. in the cockpit, to display that a manualvalve actuating command was given in regard to an ACT valve. Further,each time a valve actuating command has occurred it must be checkedwhether the respective valve is in fact actuated in accordance with thevalve actuating command. Finally, there is a need to check whether theACT valves assume predetermined valve positions following detection ofan ACT system failure (such as, e.g., an ACT fuel transfer fault or anACT low fuel level condition).

In view of the above, it is an object of the present invention toprovide test equipment that allows easy and efficient testing of atleast certain aspects of an aircraft ACT system.

To achieve this object, the present invention provides test equipmentfor testing an ACT system of an aircraft, the ACT system comprisingcontrol means configured to perform functions of an Auxiliary FuelManagement Computer (AFMC) and an Auxiliary Level Sensing Control Unit(ALSCU), wherein the test equipment comprises at least one test moduleadapted for coupling to the ACT system in place of at least a portion ofthe control means, the test module comprising means for generating oneor more test signals and outputting the test signals to the ACT system.

The test module preferably comprises switch means for switching on andoff the one or more test signals. The switch means may be manuallyoperable. In addition or in the alternative, the test equipment mayinclude test program software for execution by a processor, wherein thetest program software is so configured as to effect the generation ofone or more predetermined test signals or one or more predetermined testsignal sequences output by the test module.

In a simple embodiment, the test signals may be high or low electricpotential signals with the low state corresponding to a ground potentialand the high state corresponding to a positive or negative electricpotential different from the ground potential. In particular, the highpotential may correspond to a supply voltage level of an on-boardelectric supply voltage system of the aircraft, and the test module mayobtain the high potential from the on-board electric supply voltagesystem. Of course, the test equipment may also include its own source ofelectric voltage independent of the on-board electric supply voltagesystem.

In one embodiment, the test equipment comprises a first test moduleadapted for coupling to the ACT system in place of a portion of thecontrol means performing AFMC functions, wherein the first test modulecomprises means for generating one or more test signals simulating oneor more ACT valve commands. This embodiment may be useful for testingproper operation of various ACT valves.

The one or more simulated ACT valve commands may specifically comprise:

-   -   an ACT inlet valve command in relation to each of one or more        ACT inlet valves, and/or    -   an ACT air shutoff valve command, and/or    -   an ACT vent valve command, and/or    -   an ACT refuel valve command.

The first test module may further comprise means for generating one ormore test signals simulating at least one of a predetermined AFMCtransfer fault condition and a predetermined AFMC low-level condition.

The first test module may also comprise means for receiving one or moreACT valve condition signals representing open and closing conditions ofone or more ACT valves, wherein the first test module further comprisesfirst indicating means for visually indicating one or more ACT valveconditions.

The first indicating means may be specifically configured to indicate:

-   -   an ACT inlet valve condition in relation to each of one or more        ACT inlet valves, and/or    -   an ACT air shutoff valve condition, and/or    -   an ACT vent valve condition, and/or    -   an ACT fuel isolation valve condition, and/or    -   an ACT transfer valve condition, and/or    -   an ACT vent isolation valve condition.

Advantageously, the first indicating means include two LEDs in relationto each of) one or more ACT valves, one of the LEDs indicating, whenilluminated, an open valve position and the other indicating, whenilluminated, a closed valve position. For example, the one LED may begreen and the other red.

The first test module may comprise second indicating means forindicating generation of one or more ACT valve commands effected throughmanual operation of one or more valve operating elements provided in acockpit of the aircraft.

In another embodiment, the test equipment comprises a second test moduleadapted for coupling to the ACT system in place of a portion of thecontrol means performing) ALSCU functions with another portion of thecontrol means performing AFMC functions left in place in the ACT system,wherein the second test module comprises means for generating one ormore test signals simulating one or more ACT fuel level indications.This embodiment is useful, inter alia, for testing proper functioning ofthe AFMC portion of the control means.

Particularly, the second test module may comprise a two-position switchin relation to each of one or more additional center fuel tanks togenerate one or more test signals simulating wet and dry fuel tankconditions.

The second test module may also comprise means for generating one ormore test signals simulating:

-   -   a valve command for actuating a first servo motor of a fuel        isolation valve, and/or    -   a valve command for actuating a second servo motor of the fuel        isolation valve, and/or    -   a valve command for actuating a first servo motor of a vent        isolation valve, and/or    -   a valve command for actuating a second servo motor of the vent        isolation valve.

Regarding the above, it should be appreciated that at least some of themany valves typically found in an ACT system may be implemented with twoindependent servo actuators (servo motors) in order to provideredundancy. An exception may be the refuel valve which is oftentimesequipped with a single servo actuator only.

Further, the second test module may comprise means for generating one ormore test signals simulating:

-   -   a pipe damage indication, and/or    -   a warning wire circuit closing command, and/or    -   a predetermined ACT transfer-fault condition.

The second test module may also comprise indicating means for indicatingwhether or not the warning wire circuit is closed and/or whether anemergency power supply of the aircraft is operative.

The present invention will now be explained in more detail withreference to the enclosed drawings, in which:

FIG. 1 is a schematic plan view of an additional center tank fuel systemin an aircraft,

FIG. 2 shows a front panel of a test box for simulating ACT valvecommands, and

FIG. 3 shows a front panel of a test box for simulating ALSCU signals.

FIG. 1 shows a schematic plan view of the general arrangement of a fueltank system of a commercial passenger or cargo aircraft according to anexemplary embodiment. The fuel tank system comprises a main tank systemand an additional center tank system (ACT system). The ACT system isgenerally designated 10 in the figure. The main tank system may comprisea left wing tank 12, a right wing tank 14 and a center tank 15.

In the illustrated embodiment, the aircraft is fitted with six ACTsdesignated 16, 18, 20, 22, 24 and 26. The ACTs 16-26 are located in acargo area of the fuselage of the aircraft and are connected to eachother via a fuel line 28. They are further connected to the main wingtanks 12, 14 and the center tank 15 via a fuel line 30. The fuel line 30is the main refuel/defuel line.

Each additional center tank (ACT) 16-26 is provided with a fuelinlet-valve 32, 34, 36, 38, 40, 42, respectively.

A refuel valve 44 allows refueling of the ACT system. During refueling,the refuel valve 44 is set to an open position and will be closed at allother times.

An ACT transfer fuel pump 46 and an ACT transfer valve 48 provide amechanism for transferring fuel between the main tank system and the ACTsystem 10. Such fuel transfer occurs not only during refueling, but alsoduring flight when the fuel loaded by the aircraft is progressivelyburnt starting with the ACT fuel. To this end, the ACT fuel may betransferred via the fuel line 30 to the main center tank 15 in a mannerof sequentially emptying one ACT after another.

In order to allow venting of the ACT-system, a vent conduit 50 connectedto all additional center tanks 16-26 and coupled to a center tank ventline 52 is provided. Vent valves not shown in FIG. 1 allow selectiveventing of the additional center tanks 16-26.

When fuel is drawn from the additional center tanks 16-26, pressurizedair is fed into the additional center tanks to prevent the formation ofa potentially explosive gaseous mixture in the additional center tanks.The pressurized air is routed via an air shutoff valve 54 arranged in anair pressurization line 56 into additional center tanks 16 and 22. Sinceall ACTs 16-26 are in fluid communication with each other via ventconduit 50, the pressurized air fed into ACTs 16 and 22 will also be fedinto the remaining ACTs 18, 20, 24 and 26.

Control of the ACT system 10 is effected by an Auxiliary Fuel ManagementComputer (AFMC) operating together with an Auxiliary Level SensingControl Unit (ALSCU) not shown in the figures. Prior to delivery of anew aircraft to a customer and also in regular maintenance procedures,the entire ACT system 10 including its valves and the AFMC should betested to ensure proper operation of the system.

FIG. 2 shows an exemplary and non-limiting embodiment of a front panel58 of a test box adapted for simulating ACT valve commands. The test boxreplaces the AFMC. In other words, to bring the test box into use, theAFMC must first be disconnected from the ACT system 10. The test box maythen be connected to the ACT system 10 using the same electric connectorinterface to which the AMFC was connected.

In the left upper part of the illustrated front panel 58, a vertical rowof six manually operable, two-position (on/off) switches 60, 62, 64, 66,68, 70 is provided. Of these, switch 60 is for simulating an ACT inletvalve command to the fuel inlet valve 32 associated to ACT 16, switch 62is for simulating an ACT inlet valve command to the fuel inlet valve 34associated to ACT 18, and so forth. Actuating the switches 60-70 to movetheir operating levers to the right-side position as shown in FIG. 2corresponds to simulating an “open” command, i.e., a command that willcause the ACT inlet valves to move open. Moving the switch operatinglevers to the left in FIG. 2, on the other hand, corresponds tosimulating a “close” command to the ACT inlet valves.

To the right of the switches 60-70 there is provided on the front panel58 a vertical row of LEDs 72-82 to indicate whenever an ACT inlet valve“open” command has been manually initiated from a valve command panel(not shown herein) in the cockpit of the aircraft. Thus, a test personhas two options for testing the ACT inlet valves, one by simulatingvalve commands using the switches 60-70 of the test box of FIG. 2 andanother by manipulating on the valve command panel in the cockpit. Inletvalve commands so generated from the cockpit valve command panel arerouted to the test box via the mentioned connector interface of the ACTsystem 10.

In order to easily verify whether an ACT inlet valve command (whetherfrom the test box or from the cockpit valve command panel) has causedthe respective ACT inlet valve to assume the desired position, twovertical rows of LEDs are provided to the right of the row of LEDs72-82. These two vertical rows indicate open and shut inlet valveconditions of the inlet valves 32-42. A first row of LEDs 84-94 consistsof six red LEDs which, when illuminated, indicate that the respectiveinlet valves are in the closed position. A second row of LEDs 96-106consists of six green LEDs which, when illuminated, indicate that therespective inlet valves are in the open position.

Below the row of switches 60-70, a further set of five manuallyoperable, two-position (on/off) switches 108-116 are arranged in avertical row. These may be used for simulating an air shutoff valvecommand (switch 108), a vent valve command (switch 110), a refuel valvecommand (switch 112), an AFMC transfer fault condition (switch 114) andan ACT low fuel level condition (switch 116). While switches 108 and 112operate in the same way as switches 60-70, switch 110 is reversed inthat the “open” command corresponds to the left position of the switchoperating lever while the “close” command corresponds to the rightposition of the switch operating lever.

Right-hand of the switches 108-116 there are located on the front panel58 two further vertical rows of LEDs indicating, in a similar manner asdescribed above in connection with the LEDs 72-82 and the LEDs 84-94,the valve position of the ACT transfer valve 48, the air shutoff valve54, a vent valve, a fuel isolation valve and a vent isolation valve.

When an AFMC transfer fault condition (as may be caused, e.g., byfailure of the transfer fuel pump 46 and/or the transfer valve 48) issimulated by setting switch 114 to its right position, at least aportion of the ACT valves depicted on the front panel 58 should beautomatically moved to certain predetermined positions. By checkingwhich of the various LEDs on the front panel 58 are illuminated, it canbe verified whether or not these predetermined valve positions have beenattained.

FIG. 3 shows an exemplary and non-limiting embodiment of a front panel138 of a test box adapted for simulating ALSCU signals. This test boxreplaces the ALSCU. In other words, to bring the test box into use, theALSCU must first be disconnected from the ACT system 10. The test boxmay then be connected to the ACT system 10 using the same electricconnector interface to which the ALSCU was connected.

In an upper part of the front panel 138, an LED 140 is located which,when illuminated, indicates that an emergency power supply whichdelivers a predetermined electric voltage to the test box is operatingproperly. The emergency power supply (not shown) includes a timer-relaywhich may be set to a predefined time, e.g., 20 seconds. If thetimer-relay functions properly, the LED 140 should be illuminated for 20seconds and then turn off.

Further, a horizontal row of manually operable switches 146-156 belowthe LEDs 142, 144 serve to simulate predetermined fuel level indicationsignals for each ACT. The switches 146-156 are two-position (on/off)switches to simulate “wet” and “dry” ACT level conditions. Using theswitches 146-156 it is possible to check whether the AFMC, which is leftin place in the ACT system during use of the ALSCU substitute test box,operates correctly, i.e., causes a predetermined reaction. For example,the AFMC may be required to cause a visual indication of the fuel levelson a cockpit display panel.

Below the horizontal row of switches 146-156, there is provided on thefront panel 138 a vertical row of two-position (on/off) switches158-170. Switch 158, if set to “on”, simulates an actuating command fora first servo motor of an isolation valve located in a fuel line. Switch160, if set to “on”, simulates an actuating command for a first servomotor of a vent valve. Switch 162, if set to “on”, simulates anactuating command for a second servo motor of the fuel isolation valve,and switch 164 may be used to simulate an actuating command for a secondservo motor of the vent valve. It can then be checked whether the AFMCcauses a corresponding cockpit display and whether the correspondingvalves assume a position corresponding to the actuating command.

Switch 166, if set to “on”, simulates a damaged vent conduit. It canthen be checked whether the AFMC causes a corresponding cockpit display.Switch 168, if set to “on”, simulates an ALSCU output signal indicating,e.g., a failure of the fuel transfer pump 46. One can thus check whetherthe AFMC causes a corresponding cockpit display.

Finally, switch 170, if set to “on”, simulates a closing command toclose a warning wire circuit provided to detect a damaged vent conduit.LED 172 provided to the right of switch 170 is illuminated if thewarning wire circuit is successfully closed.

1-15. (canceled)
 16. Test equipment for testing an additional centertank (ACT) system of an aircraft, the ACT system comprising controlmeans configured to perform functions of an Auxiliary Fuel ManagementComputer (AFMC) and an Auxiliary Level Sensing Control Unit (ALSCU),wherein the test equipment comprises at least one test module adaptedfor coupling to the ACT system in place of at least a portion of thecontrol means, the test module comprising means for generating one ormore test signals and outputting the test signals to the ACT system,wherein the at least one test module comprises at least one of: a firsttest module adapted for coupling to the ACT system in place of a portionof the control means performing AFMC functions, wherein the first testmodule comprises means for generating one or more test signalssimulating one or more ACT valve commands; and a second test moduleadapted for coupling to the ACT system in place of a portion of thecontrol means performing ALSCU functions with another portion of thecontrol means performing AFMC functions left in place in the ACT system,wherein the second test module comprises means for generating one ormore test signals simulating one or more ACT fuel level indications. 17.The test equipment of claim 16, wherein at least one of the first andsecond test modules comprises switch means for switching on and off theone or more test signals.
 18. The test equipment of claim 17, whereinthe switch means are manually operable.
 19. The test equipment of claim16, wherein the one or more simulated ACT valve commands comprise: anACT inlet valve command in relation to each of one or more ACT inletvalves, and/or an ACT air shutoff valve command, and/or an ACT ventvalve command, and/or an ACT refuel valve command.
 20. The testequipment of claim 16, wherein the first test module comprises means forgenerating one or more test signals simulating at least one of apredetermined AFMC transfer fault condition and a predetermined AFMClow-level condition.
 21. The test equipment of claim 16, wherein thefirst test module comprises means for receiving one or more ACT valvecondition signals representing open and closing conditions of one ormore ACT valves, wherein the first test module further comprises firstindicating means for visually indicating one or more ACT valveconditions.
 22. The test equipment of claim 21, wherein the firstindicating means are configured to indicate: an ACT inlet valvecondition in relation to each of one or more ACT inlet valves, and/or anACT air shutoff valve condition, and/or an ACT vent valve condition,and/or an ACT fuel isolation valve condition, and/or an ACT transfervalve condition, and/or an ACT vent isolation valve condition.
 23. Thetest equipment of claim 21, wherein the first indicating means includetwo LEDs in relation to each of one or more ACT valves, one of the LEDsindicating, when illuminated, an open valve position and the otherindicating, when illuminated, a closed valve position.
 24. The testequipment of claim 23, wherein the one LED is green and the other LED isred.
 25. The test equipment of claim 16, wherein the first test modulecomprises second indicating means for indicating generation of one ormore ACT valve commands effected through manual operation of one or morevalve operating elements provided in a cockpit of the aircraft.
 26. Thetest equipment of claim 16, wherein the second test module comprises atwo-position switch in relation to each of one or more additional centerfuel tanks to generate one or more test signals simulating wet and dryfuel tank conditions.
 27. The test equipment of claim 16, wherein thesecond test module comprises means for generating one or more testsignals simulating: a valve command for actuating a first servo motor ofa fuel isolation valve, and/or a valve command for actuating a secondservo motor of the fuel isolation valve, and/or a valve command foractuating a first servo motor of a vent isolation valve, and/or a valvecommand for actuating a second servo motor of the vent isolation valve.28. The test equipment of claim 16, wherein the second test modulecomprises means for generating one or more test signals simulating: apipe damage indication, and/or a warning wire circuit closing command,and/or a predetermined ACT transfer-fault condition.
 29. The testequipment of claim 28, wherein the second test module comprisesindicating means for indicating whether or not the warning wire circuitis closed.
 30. The test equipment of claim 16, wherein the second testmodule comprises indicating means for indicating whether an emergencypower supply of the aircraft is operative.